Knowra Muscle spindle Muscle spindle A sensory receptor embedded in skeletal muscle that detects muscle length and changes in length. Its signals help regulate stretch reflexes and ongoing muscle tone.
Intrafusal muscle fiber : A small muscle fiber inside a muscle spindle, specialized for sensing stretch rather than producing substantial force. These fibers form the spindle’s central sensory apparatus and its contractile ends adjust sensitivity.
Proprioception : The sense of the body’s position and movement, arising from receptors in muscles, tendons, joints, and skin. Muscle spindles supply a major source of proprioceptive information about limb movement.
Deep tendon reflex : A clinical reflex elicited by briefly stretching a muscle through percussion of its tendon. The tap stretches the muscle and activates spindle-driven spinal reflex circuitry.
Golgi tendon reflex : A spinal response associated with Golgi tendon organ input that can reduce activation of the same muscle. It is linked to tendon tension feedback, contrasting with spindle-triggered stretch excitation.
Group Ia sensory fiber : A large, fast sensory axon that carries information about muscle stretch and its rate of change. Its primary endings wrap around spindle fibers and report rapid changes in length.
Skeletal muscle : Voluntary, striated muscle attached to the skeleton or other structures and responsible for movement. Spindles are embedded among the force-producing fibers of skeletal muscle.
Patellar reflex : The knee-jerk reflex produced by tapping the patellar tendon and briefly stretching the quadriceps muscle. It is a familiar example of a spindle-mediated stretch reflex.
Extrafusal muscle fiber : A force-producing skeletal muscle fiber located outside the muscle spindle. Unlike intrafusal fibers, extrafusal fibers generate most of the muscle’s contractile force.
Group II sensory fiber : A sensory axon that carries information mainly about sustained muscle length. Its secondary spindle endings contribute a steadier signal about the muscle’s current length.
Muscle tone : The ongoing, low-level resistance of muscles to passive stretch, maintained partly by neural activity. Spindle feedback helps sustain the reflex activity underlying resting tone.
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